The present invention relates to a semiconductor device, and more specifically, to a semiconductor device including a fuse pattern formed as a conductive polymer layer having a low melting point which can be easily cut at low temperature to improve repair efficiency.
In manufacturing semiconductor devices, if even one of many cells of the device has a defect, the device can not serve as a memory and is treated as defective.
However, it is inefficient in terms of yield to disuse the device because a cell of the memory has a defect.
A redundancy cell which is previously installed in the memory device is used to replace a defective cell to repair the entire memory, thereby improving yield.
The repair method using a redundancy cell includes replacing a normal word line having a defect or a normal bit line having a defect with a redundancy word line or a redundancy bit line which is disposed in each cell array.
When a defective cell is found through a test after processing a wafer, an internal circuit performs a program for replacing an address corresponding to the defective cell with an address of a redundancy cell. As a result, an address signal corresponding to the defective cell in its actual use is inputted to access data of the redundancy cell.
Generally, the program system includes burning and blowing a fuse with a laser beam to replace a path of an address. As a result, a common memory device includes a fuse unit configured to replace an address path by irradiating and blowing a fuse with a laser. A fuse refers to a line cut by irradiation by a laser, and a fuse box refers to the cut site and its surrounding region.
The fuse unit has a plurality of fuse sets. One fuse set can replace an address path. The number of fuse sets in the fuse box is determined by the number of redundancy word lines or redundancy bit lines in the memory device.
In general, a method for fabricating a semiconductor device includes forming an interlayer insulating film planarized over a fuse region of a semiconductor substrate, forming a metal fuse over the interlayer insulating film, and forming an insulating film and a protective film over the semiconductor substrate to cover the metal fuse.
A part of the protective film and the insulating film is etched to form a fuse open region so that a given thickness of the insulating film remains over the metal fuse of a local blowing region. The fuse open region is irradiated with a laser, and a blowing process is performed to cut a given metal fuse.
Since the insulating film has a property such as glass, laser energy is not absorbed in the insulating film but passed through the insulating film. As a result, most of the laser energy is absorbed into the metal fuse. The metal fuse is thermally expanded by the laser energy, and the insulating film surrounding the metal fuse is broken when the thermal expansion reaches a critical point. As a result, the metal fuse is instantly vaporized and physically cut.
However, an efficient repair process cannot be performed because the excellent thermal conductivity of the metal fuse is disperses the laser energy in the blowing process. Stress caused when the insulating film is broken may affect a chip. Also, it is difficult to control fuse cutting because the laser energy is changed depending on a thickness of the insulating film that remains over the metal fuse. Moreover, it is difficult to regulate the required thickness of the insulating film remaining over the metal fuse due to a step difference in one wafer.